1. Field of the Invention
The present invention relates to an image forming apparatus, a method for controlling the same, and a storage medium.
2. Description of the Related Art
In recent years, an image forming apparatus with a power saving mode has been commonly used. The image forming apparatus with the power saving mode realizes the power saving mode such that a power supplied to a main control unit for controlling the image forming apparatus is made smaller than the one supplied in a normal mode or is cut off when the image forming apparatus is in a non-standby state. A function called “proxy response” has been known in which a sub control unit realizes a network response in substitution for the main control unit with the power saving mode maintained. A resource available in the power saving mode is limited and it is impossible to perform all network responses by the proxy response. Japanese Patent Application Laid-Open No. 2010-160565, for example, discusses a technique which measures the amount of work performed by each CPU in a system including a plurality of central processing units (CPU) to predict the usage rate of each CPU based on the measured amount of work. If a CPU expected to be in an idle state exists, the technique realizes a scheduler function to save power by reducing the supply of power to the CPU.
In the technique discussed in Japanese Patent Application Laid-Open No. 2010-160565, if it is impossible to perform the network response using the proxy response function in a power saving state, a controller returns from the power saving mode to a standby state and starts monitoring the load state of a system. After that, a measurement time for measuring a load on a specific CPU is needed and a clock cannot be switched unless the measurement time elapses. For this reason, even though the load on the specific CPU is zero during the measurement time, the clock to the specific CPU cannot be switched, resultantly causing a problem that a wasteful power is consumed during the time for measuring the load on the specific CPU. Even in a case where the network response is ended in a standby state of the controller and then transition is performed to the power saving mode, the load on the CPU also needs to be measured to make it impossible to quickly transition the state, which consumes a wasteful power.